1. Technical Field
The present invention relates to a non-contact communication medium in which a loop antenna made of a conductor is formed on a circuit board and in which a communication circuit is mounted on the circuit board, more specifically, to a non-contact communication medium suitable for facilitating the production and for preventing cracking in the loop antenna, furthermore to a non-contact communication medium suitable for recycling, for facilitating the production, and for preventing cracking in a bridge coupling part of the loop antenna, and even furthermore to a non-contact communication medium suitable for improving the antenna efficiency and for easily adjusting the resonance frequency of the communication circuit.
2. Related Art
Conventionally, for example, an electronic tag disclosed in Japanese Unexamined Patent Application Publication No. 9-198481 (hereinafter, referred to as a first conventional example), a remote card disclosed in Japanese Unexamined Patent Application Publication No. 11-328343 (hereinafter, referred to as a second conventional example), and a non-contact IC card disclosed in Japanese Unexamined Patent Application Publication No. 2000-57289 (hereinafter, referred to as a third conventional example) are included in non-contact IC tags for RFID (Radio Frequency IDentification) or the like.
In the first conventional example, since each conducting part of a transmitting and receiving antenna of the electronic tag is formed by conductive paste, man-hours for assembling a responder, the thickness, and the cost are reduced as compared with an electronic tag using a known coil antenna made of a copper wire. Also, for the formation of a loop antenna, an insulating resin layer is provided on a first conducting part between the innermost circumference and the outermost circumference of the first conducting part arranged in a spiral form, and a second conducting part for connecting the innermost circumference to an IC chip is provided on the insulating resin layer. Thus, a thin and low-cost electronic tag provided with a loop antenna can be realized.
In the second conventional example, the remote card comprises a single-sided flexible circuit board, an LSI mounted on the single-sided flexible circuit board, and an antenna circuit formed on the signal-sided flexible circuit board. One end of the antenna circuit is connected to the LSI. The remote card also comprises one land formed on the single-sided flexible circuit board and connected to the other end of the antenna circuit, a foldable arm member provided on the single-sided flexible circuit board, and the other land formed on the arm member and connected to the LSI through a circuit pattern. Folding the arm member causes the one land to be connected to the other land. Accordingly, easy and low-cost production can be achieved.
In the third conventional example, the non-contact IC card comprises an antenna pattern, a pattern A, and an IC that are formed on a front surface of an antenna sheet. The non-contact IC card also comprises a slit A formed in the antenna sheet and located in a position near the other end of the antenna pattern and slits B and C formed in the antenna sheet and located in positions near the other end of the pattern A. The slit A is provided to fold the antenna sheet in such a manner that the other end of the antenna pattern is located at the rear surface of the antenna sheet and below the other end of the pattern A. The slits B and C are provided to electrically connect the other end of the antenna pattern to the other end of the pattern A by threading the leading edge of the folded bridge part from the rear surface to the front surface. Accordingly, easy and low-cost production can be achieved.
Also, conventionally, non-contact IC tags for RFID (Radio Frequency IDentification) or the like are widely known in which a loop antenna made of a conductor is formed on a circuit board and in which an IC chip is mounted on the circuit board, the loop antenna being connected to antenna connection parts of the IC chip. Here, the IC chip is, in general, mounted on the circuit board through an anisotropic conductive sheet or the like. Technologies for mounting an IC chip on a circuit board through an anisotropic conductive sheet or the like are, for example, disclosed in Japanese Unexamined Patent Application Publication No. 2000-113144 (hereinafter, referred to as a fourth conventional example), Japanese Unexamined Patent Application Publication No. 2000-323626 (hereinafter, referred to as a fifth conventional example), and Japanese Unexamined Patent Application Publication No. 2000-339427 (hereinafter, referred to as a sixth conventional example).
In the fourth conventional example, a non-contact IC card comprises a circuit board provided with an antenna coil and an IC chip arranged on the circuit board. The IC chip is arranged so as to straddle the antenna coil. The width of at least a part of the antenna coil is reduced so that the distance between a connection terminal at the inner circumference and a connection terminal at the outer circumference of the antenna coil is approximately equal to the distance between connection bumps of the IC chip, the bumps being provided to be connected to the connection terminals. Part of a plurality of traces of the antenna coil, which is straddled by the IC chip, is arranged so as to avoid portions that interfere with information transmission. The connection terminals of the antenna coil are directly connected face-down to the connection bumps of the IC chip, with an anisotropic conductive adhesion layer therebetween.
In the fifth conventional example, a semiconductor module comprises a bare IC chip, a lead terminal directly connected to a pad part of the IC chip, and sealing resin for coating around the IC chip including part of the lead terminal. At the rear surface of the IC chip, a thin resin film is formed only on a peripheral part including an edge part and a chip exposing part that is uncoated with the sealing resin is arranged at the center. The entire peripheral surface of the IC chip is coated with the sealing resin.
In the sixth conventional example, for stress relief and protection of a lead connection part, an IC chip with a lead is sealed with resin in such a manner that the shape of the sealed chip part is curved. For the stress relief against a concentrated load and a bend load, combined sealing is performed using a high elastic modulus resin for an inner layer sealing resin and using a low elastic modulus resin for an outer layer sealing resin. The sealing length of the inner layer sealing resin is set to be longer than that of the outer layer sealing resin, thus preventing the disconnection of lead wiring.
Also, conventionally, in non-contact IC tags for RFID (Radio Frequency IDentification) or the like, the resonance frequency of a non-contact IC tag must be adjusted to the resonance frequency of a responder, due to variations or the like of the characteristics of a loop antenna and an IC constituting the non-contact IC tag. Technologies for such an adjustment are disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2001-10264 (hereinafter, referred to as a seventh conventional example), Japanese Unexamined Patent Application Publication No. 2002-7985 (hereinafter, referred to as an eighth conventional example), and Japanese Unexamined Patent Application Publication No. 2002-288611 (hereinafter, referred to as a ninth conventional example).
In the seventh conventional example, a non-contact IC card capable of non-contact communication with an external reader/writer comprises a resonance circuit in a circuit board of the card, the resonance circuit including an antenna coil and a planar adjusting resistor. Adjustment of the resistance of the adjusting resistor in the resonance circuit enables adjustment of the sharpness (Q) of the resonance circuit to ensure good communication conditions. Furthermore, provision of an adjusting capacitor enables adjustment of the resonance frequency. In order to adjust the antenna characteristics, part of a plurality of circuits arranged so as to be branched off from the antenna coil is cut, thereby adjusting the sharpness.
In the eighth conventional example, a card circuit board made of a polyvinyl chloride resin sheet or the like, a wire-wound antenna coil provided on the card circuit board, a resonance frequency adjusting part provided at the leading edge of the antenna coil, and polyvinyl chloride resin sheets bonded to the top and bottom of the resin circuit board by means of heat lamination processing are provided. A conductive layer is formed on the surface of the resin sheet provided on the upper side of the resin circuit board in such a manner that the conductive layer overlaps capacitor patterns that constitute the resonance frequency adjusting part and that are formed on the resin circuit board. Forming a capacitor by the capacitor patterns and the conductive layer and adjusting the capacitance enables adjustment of the resonance frequency of the non-contact IC card.
In the ninth conventional example, a non-contact IC module, a wound copper wire antenna connected to the IC module and performing communication with an external communication apparatus, and a capacitor for changing the resonance frequency of the antenna are provided. The capacitor is formed by the copper wire antenna, and its capacitance is adjusted by the interval (pitch) of the copper wires.
However, in the first conventional example, since the insulating resin layer is provided on the first conducting part between the innermost circumference and the outermost circumference of the loop antenna and the second conducting part for connecting the innermost circumference to the IC chip is provided on the insulating resin layer, there is a problem in that the complicated production process makes the production difficult.
Also, in the second and third conventional examples, the structure in which an arm part comprising a conducting part for connecting the other end of the loop antenna to the IC chip is provided and in which collapsing the arm part causes the other end of the loop antenna to be connected to the IC chip causes a problem that stress applied to the folding part of the arm part of the loop antenna is likely to cause cracking.
Also, in view of recycling non-contact IC tags for RFID or the like, the following problems may occur in the fourth to sixth conventional examples described above in which an IC chip is mounted on a circuit board through an anisotropic conductive sheet or the like. First, since an IC chip on which data is stored is mounted on a circuit board, data may be leaked out in the process of recycling. Thus, it is desirable that the IC chip be removable from the circuit board in recycling. Second, although a loop antenna portion is easy to recycle due to its uncomplicated structure, an IC chip must be removed in order to recycle only the loop antenna portion, and this results in more problems.
Also, in the seventh to ninth conventional examples, a capacitor part of a resonance circuit provided inside of a card circuit board interferes with electromagnetic waves, thus causing a problem that the sharpness (Q value) is reduced.
Also, in the sixth conventional example described above, since the capacitance is adjusted by a pitch between the copper wires, there is a problem in that various types of circuit boards must be prepared depending on the pitch.
Accordingly, the present invention is designed by focusing on such problems of the conventional technologies, and a first object of the present invention is to provide a non-contact communication medium suitable for facilitating the production and for preventing cracking in a loop antenna.
Also, a second object of the present invention is to provide a non-contact communication medium suitable for recycling, for facilitating the production, and for preventing cracking in a bridge coupling part of the loop antenna.
Furthermore, a third object of the present invention is to provide a non-contact communication medium suitable for improving the antenna efficiency and for easily adjusting the capacitance of a capacitor in a resonance circuit.